1. Field of the Invention
The present invention generally relates to magnetic head sliders in which magnetic heads are embedded, and more particularly to an apparatus and method for producing magnetic head sliders.
2. Description of the Related Art
A magnetic hard disk unit is widely used as an external storage unit. The magnetic hard disk unit includes a plurality of magnetic head sliders in which a plurality of heads are embedded. The magnetic head sliders fly over magnetic disks which are rotating. Recently it has been required that the flying height of the magnetic head sliders be reduced in order to improve sensitivity of the magnetic heads. For this requirement, it is necessary to form the slider surfaces so that they have a flatness less than or equal to 1/30 .mu.m. The magnetic head sliders start to take off from the magnetic disks and fly when enabled, and come into contact with the magnetic disks when disabled. The above-mentioned magnetic head sliders are called contact start stop type (hereinafter simply referred to as a CSS type) magnetic head sliders. In the CSS type magnetic head sliders, it is desired that the magnetic heads be prevented from being damaged during takeoff and landing.
FIG. 1A is a perspective view of a first conventional magnetic head slider 1A. The magnetic head slider 1A shown in FIG. 1A includes two flat rail (slider) surfaces 2a and 2b. Taper portions 3a and 3b are formed in leading ends (air incoming side) of the rail surfaces 2a and 2b, respectively. As shown in FIG. 1C, two thin film magnetic heads 4a and 4b are embedded in trailing end portions (air outgoing side) of the rail surfaces 2a and 2b, respectively. It is desired that each of the rail surfaces 2a and 2b has a flatness less than or equal to 1/30 .mu.m in order to minimize the distance between the rail surfaces 2a and 2b and a recording surface of the magnetic disk. The tapered portions 3a and 3b may be omitted, and one of the two magnetic heads may be omitted.
FIG. 1B is a perspective view of a second conventional magnetic head slider 1B. It is required to reduce friction between the magnetic head slider 1B and the magnetic disk and wearing thereof and to reduce the possibility that a head may be crushed. In order to meet the above requirements, rail surfaces 5a and 5b of the magnetic head slider 1B are formed into a convex shape. Such convex surfaces are called crown shapes. It is desired that a crown quantity (difference of elevation), which can be expressed by the difference between the lowest level (reference level) and the highest level on the crown surface, be equal to or larger than 10-20 nm.
The actual rail surfaces of many of the sliders produced have errors in flatness due to twists or negative crown shapes. These poor shapes of the rail surfaces are mainly due to imbalance in the stress between the front and back surfaces of the sliders caused by mechanical processing. In order to obtain the rail surfaces having desired shapes, it is necessary to perform a process for correcting the rail surfaces.
As will be described in detail later, the present invention is intended to efficiently and effectively process the rail surfaces of sliders, so that desired ideal shapes of the rail surfaces can be obtained. The ideal shapes means that the rail surfaces has a good flatness (a PV (peak-to-valley) value of 30 nm or less) and a crown quantity equal to or greater than 10 nm, a small recession of a magnetic pole (also referred to as a recess quantity) (equal to or less than about 20 nm) and a small gap depth (0.5-1.5 .mu.m).
A conventional process for correcting the deformed rail surfaces of the sliders will now be described below with reference to FIGS. 2 and 3.
FIG. 2 is a diagram showing a conventional slider production process. Back surfaces of a plurality of magnetic head sliders 1A are fastened, by means of an adhesive, to a work member 6 made of a rigid member, and the flat rail surfaces 2a and 2b of the sliders 1A are placed on a ring-shaped lapping base 7. A predetermined pressure is vertically applied to the work member 6 is means of a weight or the like. In this state, the lapping plate 7 is rotated around an axis O in a direction indicated by an arrow while the work member 6 is rotated in a direction indicated by another arrow.
However, it should be noted that the thicknesses of the sliders 1A are slightly different from each other and that the sliders 1A are fastened to the work member 6 by means of an adhesive. Hence, the work member 6 having a great thickness is preferentially processed and the processing quantities of the respective sliders produced are different from each other. As a result, it is impossible to uniformly correct the rail surfaces of a large number of sliders.
Conventionally, as shown in FIG. 3, the sliders are manually polished one by one. However, in this manual lapping process, it is very difficult to obtain the desired crown-shaped rail surfaces. Hence, it is impossible to,,efficiently and effectively produce a large number of sliders having the desired crown-shaped rail surfaces.
It will be noted that a gap depth D shown in FIG. 1C is as small as possible in order to increase the recording density. However, it is impossible to finely adjust the gap depth D by means of the conventional techniques as shown in FIG. 2 or FIG. 3.